Vibrational properties of Ni–Mn–Ga shape memory alloy in the martensite phases
Vibrational properties of Ni–Mn–Ga shape memory alloy in the martensite phases
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马氏体相 Ni-Mn-Ga 形状记忆合金的振动性能
DOI：
10.1088/1367-2630/15/12/123016
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发表时间：
2013
影响因子：
3.3
通讯作者：
W. Petry
中科院分区：
文献类型：
--
作者：
S. Ener;T. Mehaddene;B. Pedersen;M. Leitner;J. Neuhaus;W. Petry
研究铁磁形状记忆合金系统 Ni-Mn-Ga 的声子色散可以深入了解马氏体转变的机制和驱动转变的力。单轴应力下奥氏体单晶的转变导致两种具有垂直调制矢量的马氏体变体共存。在这里，我们报告了具有非化学计量成分的马氏体晶体的非弹性中子散射研究，这些成分从非调制（NM）到五层（5M）和七层（7M）调制马氏体相。 5M 和 7M 晶体都显示出沿 [xixí?>0] 完全相称的卫星峰，对应于五层和七层调制。这些上层结构峰值成为调制结构的 Γ 点。由于（001）平面内两种变体的共存，可以观察到反映调制矢量[ xi ́? > 0 ]的新声子和对应于非调制方向的声学TA2 [ xi 0 ]声子。当从上方和下方接近马氏体-奥氏体转变时，后者在 xi = 0.2–0.4 附近表现出明显的软化，即这种软化模式在转变温度下具有最低频率。总体而言，奥氏体和马氏体相的声子色散彼此非常相似。单轴变换后两种马氏体变体的共存解释了低能激发的特殊行为，这与之前涉及电荷密度波和相关相子模式的解释形成鲜明对比。
Studying the phonon dispersion of the ferromagnetic shape memory alloy system Ni–Mn–Ga gives insight into the mechanism of the martensite transition and the forces driving the transition. Transformation of austenite single crystals under uniaxial stress results in the coexistence of two martensitic variants with perpendicular modulation vector. Here we report on inelastic neutron scattering studies of martensite crystals with off-stoichiometric compositions, varying from non-modulated (NM) to five- (5M) and seven- (7M) layer modulated martensite phases. Both the 5M and 7M crystals show fully commensurate satellite peaks along [ξξ¯?>0], corresponding to the five- and seven-layer modulation. These superstructure peaks become Γ-points of the modulated structure. Due to the coexistence of two variants within the (001) plane, both new acoustic phonons reflecting the modulation vector [ξξ¯?>0] and acoustic TA2[ξξ0] phonons corresponding to the non-modulated direction are observed. The latter display a pronounced softening around ξ = 0.2–0.4 when approaching the martensite–austenite transition from above and below, i.e. this soft mode has lowest frequency at the transition temperature. Overall the phonon dispersion of the austenite and martensite phase resemble each other very much. The coexistence of two martensitic variants after uniaxial transformation explains the particular behaviour of the low-energy excitations, in contrast to previous interpretations involving charge-density waves and associated phason modes.
影响因子：
3.7
作者：
Ener, Semih;Neuhaus, Juergen;Acet, Mehmet
通讯作者：
Acet, Mehmet